1. Field
Example embodiments relate to a storage node, a semiconductor device and methods of manufacturing the same. Other example embodiments relate to a multi-layer storage node, a resistive random access memory device including a multi-layer storage node and methods of manufacturing the same.
2. Description of the Related Art
In a semiconductor memory cell array, many memory cells may be connected through a desired circuit structure. In general, each memory cell of a dynamic random access memory (DRAM) includes a switch and a capacitor. DRAMs may be highly integrated, rapid memory devices. DRAMs do not retain data when power is cut off.
A flash memory is a representative example of nonvolatile memory devices capable of retaining data even after power is cut off. Although the flash memory is nonvolatile, the flash memory may not be as highly integrated and/or may have a lower operating speed compared to DRAMs.
For thus reasons, research has been conducted for developing other nonvolatile memory devices (e.g., magnetic random access memories (MRAMs), ferroelectric random access memories (FRAMs) and phase-change random access memories (PRAMs)) that exhibit the desired semiconductor characteristics.
MRAMs store data using variations in the magnetization direction at tunnel junctions. FRAMs store data using polarization characteristics of ferroelectricity. Research on ways to increase the integration level, increase the operating speed, increase the data retention characteristics, and/or decrease the power consumption characteristics of MRAMs and FRAMs is being conducted.
PRAMs store data using resistance variations caused by phase changes of specific materials. In general, each cell of a PRAM includes a resistor and a switch (a transistor). PRAMs may be fabricated using DRAM manufacturing equipment. Using DRAM manufacturing equipment to fabricate PRAMs may be difficult and/or takes additional time to etch. As such, the cost per device increases due to a low productivity, making it difficult to manufacture competitive products.
In general, each cell of a resistive random access memory (RRAM) includes a storage node in which a lower electrode, a resistive layer and an upper electrode may be sequentially stacked. The resistance of the resistive layer varies according to an applied voltage. The PRAM is a nonvolatile memory device that may have a more rapid operating speed. Various PRAMs are currently being researched.